Sustained release pharmaceutical compositions

ABSTRACT

Novel sustained release compositions comprising a core containing a drug, a seal coating surrounding the core and a sugar coating surround the seal coated core are disclosed.

This is a continuation-in-part of application Ser. No. 65,317, filed Aug. 9, 1979, now allowed, U.S. Pat. No. 4,248,858.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to sustained release pharmaceutical compositions and more particularly it relates to sustained release pharmaceutical compositions containing at least one drug in both an inner compressed core and an outer sugar layer.

2. Description of the Related Art

During the past few years there has been much work devoted to the development of systems which promote the release of active ingredients over a prolonged period of time. The advantages of administering orally active drugs in a sustained release formulation are numerous. If a drug is released too quickly in the stomach it can conceivably cause stomach upset. Additionally, the acid environment of the stomach may adversely affect the potency of a drug. Also the taking of medication once a day instead of numerous times a day eliminates a major source of inconvenience for the patient as well as providing for a more even distribution of drug concentration in the blood.

One example for the need for sustained release formulations is in the case of 1-(isopropylamino)-3-(1-naphthyloxy)-2-propanol (propranolol) described in U.S. Pat. No. 3,337,628. This compound is used in the treatment of coronary artery disease, migraine, anxiety, and tremors, and specifically as a β-adrenergic blocking agent. However, a major drawback of compounds disclosed in U.S. Pat. No. 3,337,628 and particularly propranolol is that because of extensive metabolism, little unchanged active material reaches the systemic circulation after oral administration. Additionally, plasma levels of propranolol show a large patient to patient variation. The preparation of a sustained release formulation containing propranolol would allow for less frequent dosing while achieving similar blood levels to those attained by administering smaller doses more frequently.

U.S. Pat. No. 4,138,475 describes a sustained release composition containing propranolol which consists of a hard gelatine capsule containing film coated spheroids. The present invention relates to a new sustained release composition which is not disclosed in, nor rendered obvious by, either of the above cited patents, nor elsewhere in the art.

SUMMARY OF THE INVENTION

According to the present invention, a sustained release composition is provided comprising a compressed core containing a drug, a seal coating surrounding the compressed core and a sugar coating surrounding the seal-coated, compressed core. In addition to a therapeutically effective amount of the drug, the core further comprises at least one pharmaceutically acceptable water soluble polymer and at least one pharmaceutically acceptable water soluble polymer and at least one pharmaceutically acceptable water insoluble polymer mixture. The core can also comprise hydroxypropyl methylcellulose and at least one of hydroxypropylcellulose and hydroxypropyl methylcellulose phthalate; with the proviso that when the water soluble polymer is only hydroxypropyl methylcellulose then the water insoluble polymer is not only ethylcellulose, and that when the water insoluble polymer is only ethylcellulose then the water soluble polymer is not only hydroxypropyl methylcellulose. The seal coating comprises a film coating selected from enteric and non-enteric materials and mixtures thereof, and the sugar coating comprises sugar and a loading dose of at least one drug contained in the core. The sugar coating may further contain additional drugs which are not present in the compressed core.

The compressed core is prepared in admixture and preferably from a granulation of the drug and other pharmaceutically acceptable excipients and the seal coating may additionally contain a plasticizer. Thus, the core drug or drugs are substantially free of coating within the compressed core itself.

DETAILED DESCRIPTION OF THE INVENTION

The sustained release composition of this invention comprises three main components: a compressed core, a seal coating surrounding the compressed core and a sugar coating surrounding the seal-coated compressed core.

The core formulation, comprises about 20% to about 70% by weight of the core of the drug or drugs for which sustanted release is desired, and about 30% to about 72% by weight of the core of the water soluble polymer(s) and the water insoluble polymer mixture. The ratio of drug to said polymers is in the range from about 0.3:1 to about 2.2:1 and preferrably from about 1:1 to about 1.5:1. Furthermore, the ratio of water soluble polymer to water insoluble polymer is from about 10:1 to about 1.5:1 and preferrably from about 5:1 or 4:1 to about 1.5:1.

The water soluble polymers are selected from pharmaceutically acceptable synthetic polymers and natural gums. Illustratively the water soluble polymer may be selected from at least one of the synthetic cellulose polymers, such as, hydroxypropyl methylcellulose, hydroxypropylcellulose and the like; and the natural gums, such as xanthan gum, karaya gum and the like.

The water insoluble polymer mixture of this invention is selected from at least one of the synthetic polymers, such as ethylcellulose or ethylcellulose and at least one of carboxypolymethylene (also known as carboxy vinyl polymer), hydroxypropyl methylcellulose phthalate and hydroxypropyl cellulose.

A suitable form of hydroxypropyl methylcellulose is that having a viscosity (2% solution) in the range of 4,000 to 40,000 cps at 20° C., and more particularly a viscosity of 15,000 cps at 20° C. A suitable form of ethylcellulose is that having a viscosity (2% solution) of 5 to 50 cps at 20° C. and more particularly a viscosity of 7 cps at 20° C. A suitable form of hydroxypropyl cellulose is that having a viscosity (2% solution) in the range of 4000 to 40,000 cps at 20° C. A suitable form of powdered gum karaya is that having a viscosity (0.5% solution) in the range of 170 to 250 cps at 25° C. A suitable form of xanthan gum is that having a viscosity (1% solution with 1% potassium chloride added) in the range of 600 to 1400 cps at 24° C. A suitable form of carboxypolymethylene is that having a viscosity (0.5% solution) in the range of 30,000 to 40,000 cps at 25° C. A suitable form of hydroxypropyl methylcellulose phthalate is that having a viscosity (15% solution in methylene chloride - methanol (1:1)) in the range of 150 to 290 cps at 20° C.

The core formulation may further contain other pharmaceutically acceptable excipients such as binders, fillers, compression aids, lubricants, granulation aids, flow aids and the like.

The seal coating is selected from one or more of those film forming materials which is capable of substantially protecting the core during its passage from the stomach to the intestines. Accordingly, depending on the overall properties required by the choice of drug in the composition of this invention, the seal coating may be selected from enteric and non-enteric film forming materials, and mixtures thereof.

The enteric coating materials are materials which are more susceptible to hydrolysis or become soluble at a pH greater than about 5. Suitable examples of such materials include polyvinylacetate phthalate (PVAP), cellulose acetate phthalate (CAP), carboxy methyl ethyl cellulose, hydroxypropyl methylcellulose phthalate, and the like. In order to minimize hardening of a particular coating (enteric or non-enteric) on aging it is often desirable to employ a plasticizer. In these latter instances the coating material may comprise about 70-100% of the seal coating, and more particularly at least 80% of the seal coating. The seal coating surrounds the compressed core and may be prepared by spray coating the tumbling, compressed cores with a solution of the seal coating.

Non-enteric film forming materials employed in the seal coating are materials which because of their solubility or the amounts (or thickness) of the applied coating substantially retard any hydration of the compressed core during its passage through the stomach. For this purpose the seal coating, whether enteric or non-enteric, must cover the entire surface of the compressed core. Non-enteric film forming materials useful for this purpose include a number of hydrocolloids which include one or more, natural, partially or totally synthetic gums. In accordance with the present invention a preferred non-enteric seal coating includes a mixture of at least two hydrocolloids, one a water soluble polymer and one a water insoluble or relatively insoluble polymer. An example of such a mixture is provided by the use of ethyl cellulose with hydroxypropyl methyl cellulose.

Other non-enteric materials useful in the seal coating include, alkyl celluloses, such as, methylcellulose and propyl cellulose; hydroxyalkyl celluloses, such as hydroxypropyl cellulose and hydroxyethyl cellulose; and the like.

The amount of seal coating necessary for protecting the core will vary depending on the surface are of the core and the efficiency of the coating equipment and operation. Satisfactory results employing 360 mg. cores have been obtained with as little as about 10 mg. of seal coating to as high as about 30 mg. It is preferred, however, that the seal coating does not add more than about 15-20 mg. to a 360 mg. core.

The seal coated, compressed cores are then sugar coated with a sugar coating suspension or solution comprising sugar and a loading dose of at least one drug contained in the core, for which sustained release properties are desired. The ratio of said drug in the sugar coating to said drug in the compressed core is in the range from about 1:15 to about 1:3, more particularly from about 1:8 to about 1:6, and preferably about 1:7. In addition to providing fast release of a therapeutically effective amount of drug and while not completely understood, it appears that the loading dose assists in achieving uniform blood levels of the core drug for which sustained release properties are desired. The sugar coating may further contain drugs not contained in the core, for which sustained release properties are not required.

It has been found that the sustained release composition of this invention appears to be more effective at densities greater than about 1.1, preferrably a density of at least 1.2 and most preferrably a density of at least 1.3. While not wishing to be bound by any theory, it is believed that the higher densities assist in minimizing stomach emptying time variations among different patients and in maintaining the composition for longer periods in the upper portions of the alimentary tract from which a drug such as propranolol is better absorbed.

The composition of this invention provides substantially zero order release of the core contained drug for about 12 hours following the first hour of administration. In the case of the β-adrenergic blocker, propranolol hydrochloride, the sustained release composition of this invention effectively provides substantially the same therapeutic efficacy for the drug as provided by the identical dosage of drug administered in divided doses, which is the standard dosage regimen.

The composition of this invention is suitable for those drugs having a short half-life (not greater than about 10-12 hours), which therefore may require frequent administration. The composition is especially suitable for water-soluble drugs and particularly for β-adrenergic blocking agents such as propranolol and its pharmaceutically acceptable acid addition salts. Suitable additional drugs employed in the sugar coating include one or more of those drugs which would be utilized in adjunct therapy with the core drug for which sustained release properties are required. For a β-adrenergic blocking agent such as propranolol such drugs include diuretics, saluretics vasodilators, alpha beta blockers, ganglionic blockers, centrally acting antihypertensives, inhibitors of the renin-angiotensin-aldosterone system and the like. Illustrative of some of these drugs are hydrochlorothiazide, triamterene, hydralazine, chlorthalidone, furosemide, other thiazide drugs, γ-[(dimethylamino)methyl]-1,3,4,9-tetrahydro-1-methylpyrano [3,4-b]indole-1-propanol and its pharmaceutically acceptable salts, spiranolactone, captopril, prazocin, isosorbide dinitrate, isosorbide-2-mononitrate, tienilic acid, and the like.

While the present invention is obviously advantageous for acid sensitive drugs and for drugs primarily absorbed from the intestines, it is to be understood that the present invention is not to be construed as being limited to any particular drug (medicament) or class of drugs. Among the various classes of drugs advantageously administered by this invention are, for example, hypertensives, analgesics, inhibitors of aldose reductase, sedatives, antiinflammatory agents, anticonvulsants, adrenergics, vitamins, antihistamines, hypotensives, antitussives, dopamine agonists and the like. Illustrative of some of these drugs are ascorbic acid, aspirin, penicillins, tetracyclines, cephalosporins, metoprolol, pseudoephedrine, chlorpheniramine maleate, 1,8-diethyl-1,3,4,9-tetrahydropyrano [3,4-b]indole-1-acetic acid (known as etodolac), dextromethorphan, primidone, phenylpropanolamine and the like.

The amount of drug contained in the sustained release compositions of this invention will vary depending on the drug or drugs employed. When, for example, the drug is propranolol hydrochloride, the composition of this invention may contain 40-320 mg., more particularly 80-160 mg.; and the amount of other drugs when employed in the sugar coating but not the core, will vary according to their therapeutically effective amounts.

The invention is further illustrated but not limited by the following examples.

EXAMPLE 1

    __________________________________________________________________________     Propranolol                                                                            160 160 160 160 160 160 160 160                                        Ethylcellulose                                                                         98  98  27.4                                                                               27.4                                                                               27.4                                                                               27.4                                                                               --  --                                         Xanthan Gum                                                                            392 --  --  49  25  --  --  --                                         Colloidal-silica                                                                       10.5                                                                               --  0.5 0.5 0.5 0.5 --  0.5                                        Karaya Gum                                                                             --  392 --  --  --  --  --  --                                         HPMC    --  --  54.7                                                                               60.5                                                                               109.5                                                                              109.5                                                                              60  109.6                                      HPC     --  --  54.7                                                                               --  --  --  14  --                                         Carbopoxy                                                                              --  --  --  --  --  12  --  --                                         polymethylene                                                                  HPMCP   --  --  --  --  --  --  --  27.4                                       Lactose 50  50  --  --  --  --  --  --                                         Stearic Acid                                                                           --  --  12.7                                                                               17  17  14  4.5 12                                         Talc    --  --  1   1   1   1   --  1                                          MCC     --  --  47  41.6                                                                               16.6                                                                               33.6                                                                               --  47.5                                       Ca Stearate                                                                            --  --  2   3   3   2   1.5 2                                          Total Core                                                                             700 700 360 360 360 360 240 360                                        Weight In mg.                                                                  __________________________________________________________________________

Compressed cores of the above formulae were prepared by single or double (wet) granulations employing either denatured 23A alcohol and/or methylene chloride, alcohol, or alcohol-water mixtures.

EXAMPLE 2

The compressed (360 mg.) cores of Example 1 are then seal coated with a sufficient amount of the following coating formulation to add approximately 30 mg. to the weight of the compressed cores after drying.

    ______________________________________                                         Polyvinylacetate phthalate (30%)                                                                       172ml                                                  Opaseal® P-28-0200                                                         Methylene Chloride      410ml                                                  Alcohol, Denatured 23 A, Anhydrous                                                                     410ml                                                  Acetylated glycerides (Myvacet® 9-40)                                                              8.0ml                                                  ______________________________________                                    

EXAMPLE 3

Dried, seal coated cores of (360 mg.) Example 2 are then coated with the following sugar coating suspension containing propranolol hydrochloride in an amount sufficient to add about 20 mg. of the propranolol.

    ______________________________________                                         Microcrystalline Cellulose                                                                        .048 kg.                                                    Sucrose            .645 kg.                                                    Water              .251 kg.                                                    Propranolol HCl    .056 kg.                                                    Titanium Dioxide   .006 kg.                                                    ______________________________________                                    

The tablets are then further coated with a sugar filler suspension, a sugar smoothing suspension, a sugar color syrup and a polishing suspension. There is thus obtained a sustained release composition containing about 160 mg. of propranolol hydrochloride in the core and 20 mg. of the drug in the sugar coating.

EXAMPLE 4

Sustained release compositions containing both propranolol HCl and hydrochlorothiazide in the sugar coating are prepared employing the following coating formulations and the seal coated cores (360 mg.) of Example 2.

    ______________________________________                                         Sucrose          .515 kg.                                                      Propranolol HCl  .053 kg.                                                      Hydrochlorothiazide                                                                             .133 kg.                                                      Calcium Carbonate                                                                               .040 kg.                                                      Water            .257 kg.                                                      ______________________________________                                    

The tablets are then further coated as in Example 3. There is thus obtained a sustained release composition of propranolol HCl containing 160 mg. of propranolol HCl in the core and 20 mg. of propranolol HCl with 50 mg. hydrochlorothiazide in the sugar coating.

EXAMPLE 5

The dried, seal coated cores of Example 2 are coated with the following sugar coating suspension and as in Example 3 in an amount sufficient to obtain a sustained release composition containing 160 mg. of propranolol HCl in the core, and containing in the sugar coating 20 mg. propranolol HCl, 50 mg. hydrochlorothiazide, and 100 mg. triamterene.

    ______________________________________                                         Sucrose          .50  kg.                                                      Triamterene      .125 kg.                                                      Hydrochlorothiazide                                                                             .062 kg.                                                      Propranolol HCl  .025 kg.                                                      Calcium Carbonate                                                                               .037 kg.                                                      Water            .250 kg.                                                      ______________________________________                                    

EXAMPLE 6

The compressed cores of Example 1 may also be seal coated with a sufficient amount of either of the following non-enteric coating formulations to add approximately 10-15 mg. to the weight of the compressed cores after drying.

    ______________________________________                                                           A        B                                                   ______________________________________                                         HPC 50 cps, USP     17.6       6.8                                             EC 7 cps, NF        5.1        6.8                                             Stearic Acid USP purified                                                                          1.3        1.4                                             Solution of methylene chloride                                                 and 23A Alcohol                                                                ______________________________________                                    

These film coated cores may then be further coated as described in Examples 3-5. 

What is claimed:
 1. A sustained release pharmaceutical composition comprising a compressed core, a seal coating surrounding the core and a sugar coating surrounding the seal coated core wherein,(a) the core comprises a drug in an amount of about 20% to about 70% by weight of the core, at least one pharmaceutically acceptable water soluble polymer selected from the group consisting of hydroxypropyl methyl cellulose, hydroxypropyl cellulose, xanthan gum and karaya gum, and at least one pharmaceutically acceptable water insoluble polymer mixture selected from the group consisting of ethylcellulose and ethyl cellulose and at least one of carboxypolymethylene, hydroxypropyl methylcellulose phthalate and hydroxypropylcellulose, said polymers in an amount of about 30% to about 72% by weight of the core; (b) the seal coating comprises a film coating material selected from the group consisting of enteric and non-enteric materials and mixtures thereof; and (c) the sugar coating comprises sugar and a loading dose of said drug contained in the core;with the proviso that when the water soluble polymer is only hydroxypropyl methylcellulose then the water insoluble polymer is not only ethylcellulose, and that when the water insoluble polymer is only ethylcellulose than the water soluble polymer is not only hydroxypropyl methylcellulose; and with the further proviso that when the seal coating consists essentially of an enteric coating material the drug is other than propranolol or its pharmaceutically acceptable salts.
 2. The composition of claim 1 wherein the ratio of said drug in the sugar coating to said drug in the core is from about 1:15 to about 1:3.
 3. The composition of claim 1 wherein the ratio of drug in the core to said polymers is from about 0.3:1 to about 2.2:1 and the ratio of water soluble polymer to water insoluble polymer is from about 10:1 to about 1.5:1.
 4. The composition of claim 1, 2 or 3 wherein the sugar coating further comprises at least one drug used in adjunct therapy with a drug in the core.
 5. The composition of claim 4 comprising about 40-320 mg. of propranolol hydrochloride; wherein the ratio of propranolol in the sugar coating to propranolol in the core is from about 1:6 to about 1:8 and wherein the ratio of water soluble polymer to water insoluble polymer is from about 5:1 to about 1.5:1.
 6. The composition of claim 5 wherein the sugar coating further comprises a therapeutically effective amount of at least one of hydrochlorothiazide and triameterene.
 7. A sustained release pharmaceutical composition comprising a compressed core, a seal coating surrounding the core and a sugar coating surrounding the seal coated core wherein,(a) the core comprises a drug in an amount of about 20% to about 70% by weight of the core, and the cellulose polymers hydroxypropyl methylcellulose and at least one of hydroxypropylcellulose and hydroxypropyl methylcellulose phthalate in an amount of about 30% to about 72% by weight of the core; (b) the seal coating comprises a film coating material selected from the group consisting of enteric and non-enteric materials and mixtures thereof; p1 (c) the sugar coating comprises sugar and a loading dose of said drug in the core;and with the proviso that when the seal coating consists essentially of an enteric coating material the drug is other than propranol or its pharmaceutically acceptable salts.
 8. The composition of claim 7 comprising about 40-320 mg. of propranolol hydrochloride and wherein the ratio of propranolol in the sugar coating to propranolol in the core is from about 1:6 to about 1:8.
 9. The composition of claim 8 in which the sugar coating further comprises at least one drug used in adjunct therapy with a β-adrenergic blocking agent.
 10. A sustained release pharmaceutical composition comprising a compressed core, a seal coating surrounding the core and a sugar coating surrounding the seal coated core wherein,(a) the core comprises a therapeutically effective amount of at least one drug in amount of about 20% to about 70% by weight of the core, at least one pharmaceutically acceptable water soluble polymer selected from the group consisting of hydroxypropyl methyl cellulose, hydroxypropylcellulose, xanthan gum and karaya gum and at least one pharmaceutically acceptable water insoluble polymer mixture selected from the group consisting of ethyl cellulose and ethylcellulose and at least one of carboxypolymethylene, hydroxypropyl methylcellulose phthalate and hydroxypropylcellulose, said polymers in amount of about 30% to about 72% by weight of the core; (b) the seal coating comprises a film coating material selected from the group consisting of enteric and non-enteric materials and mixtures thereof; and (c) the sugar coating comprises sugar and a loading dose of at least one drug contained in the core;and with the proviso that when the water soluble polymer is only hydroxypropyl methylcellulose then the water insoluble polymer is not only ethylcellulose, and that when the water insoluble polymer is only ethylcellulose then the water soluble polymer is not only hydroxypropyl methylcellulose; and with the further proviso that when the seal coating consists essentially of an enteric coating material the drug is other than propranolol or its pharmaceutically acceptable salts.
 11. The composition of claim 10 wherein the sugar coating further comprises at least one drug used in adjunct therapy with the drug contained in the core.
 12. A sustained release pharmaceutical composition comprising a compressed core, a seal coating surrounding the core and a sugar coating surrounding the seal coated core wherein,(a) the core comprises a therapeutically effective amount of at least one drug in an amount of about 20% to about 70% by weight of the core, and the cellulose polymers hydroxypropyl methylcellulose and at least one of hydroxypropylcellulose and hydroxypropyl methylcellulose phthalate in an amount of about 30% to about 72% by weight of the core; (b) the seal coating comprises a film coating material selected from the group consisting of enteric and non-enteric materials and mixtures thereof; and (c) the sugar coating comprises sugar and a loading dose of at least one drug contained in the core;and with the proviso that when the seal coating consists essentially of an enteric coating material the drug is other than propranolol or its pharmaceutically acceptable salts.
 13. The composition of claim 12 wherein the sugar coating further comprises at least one drug in adjunct therapy with the drug contained in the core. 